Bayesian networks identify determinants of outcomes following cardiac surgery in a UK population.

BACKGROUND: Traditional risk stratification tools do not describe the complex principle determinant relationships that exist amongst pre-operative and peri-operative factors and their influence on cardiac surgical outcomes. This paper reports on the use of Bayesian networks to investigate such outcomes. METHODS: Data were prospectively collected from 4776 adult patients undergoing cardiac surgery at a single UK institute between April 2012 and May 2019. Machine learning techniques were used to construct Bayesian networks for four key short-term outcomes including death, stroke and renal failure. RESULTS: Duration of operation was the most important determinant of death irrespective of EuroSCORE. Duration of cardiopulmonary bypass was the most important determinant of re-operation for bleeding. EuroSCORE was predictive of new renal replacement therapy but not mortality. CONCLUSIONS: Machine-learning algorithms have allowed us to analyse the significance of dynamic processes that occur between pre-operative and peri-operative elements. Length of procedure and duration of cardiopulmonary bypass predicted mortality and morbidity in patients undergoing cardiac surgery in the UK. Bayesian networks can be used to explore potential principle determinant mechanisms underlying outcomes and be used to help develop future risk models.

Anterior leaflet replacement and reconstruction with Admedus Cardiocel™ decellularized pericardial patch in tricuspid valve endocarditis.

We present the case of a 28 year-old lady with a history of intravenous drug use who presented to our institution with symptomatic right heart failure secondary to tricuspid valve regurgitation. She presented with infective endocarditis leading to dyspnoea and peripheral oedema secondary to torrential tricuspid regurgitation. Transthoracic echocardiography confirmed right ventricular dysfunction and congestive hepatomegaly. Intra-operatively findings an infected and destroyed anterior leaflet of the tricuspid valve with posterior leaflet prolapse was found to cause severe tricuspid regurgitation. She had complex tricuspid valve reconstruction using anterior leaflet reconstruction using Admedus Cardiocel™ patch, posterior leaflet prolapse correction and commissural reduction with a McGoon imbrication and annuloplasty ring to stabilize the repair. This case demonstrates the importance of reconstructive tricuspid valve surgery in the setting of infective endocarditis. Furthermore, this case demonstrates the possibility of anterior leaflet excision and reconstruction with an excellent durable functional result.

Delayed chylothorax in the absence of radiological evidence of rib or vertebral body fractures following blunt trauma.

Our case report illustrates effective implementation of conservative measures without the need for more invasive procedures, which can be required in refractory cases. Our patient was a 42-year-old female who fell from a horse and presented with a 1-week history of dyspnoea. Investigations revealed her to have a large right chylothorax, which was treated conservatively with chest drainage and octreotide. The patient remained in hospital for a total of 3 days prior to being discharged home without further complications. Blunt traumatic chylothorax should be considered as part of the differential diagnosis in patients who present with ongoing dyspnoea or chest discomfort within a 2-week preceding history of blunt trauma. Radiological imaging should be mandatory and the absence of posterior thoracic fractures does not exclude the diagnosis. Conservative management with pleural drainage, medium-chain triglyceride diet and octreotide yielded excellent results in our case.

Pulmonary lymphangioleiomyomatosis masquerading as unilateral heterogeneous emphysema.

Pulmonary lymphangioleiomyomatosis (LAM) is a rare, well-described pathology and usually is exclusive to females of a reproductive age. We present a 45 year-old lady who presented to the surgeons 1 year after an admission with acute dyspnoea following influenza infection. Initial computed tomography imaging findings demonstrated severe, heterogenous right-sided bullous emphysematous changes, but histopathological analysis of the post-operative specimen favoured a diagnosis of LAM. This case demonstrates the importance of considering LAM as a differential diagnosis for findings of unilateral emphysema or lobar emphysema, in which alpha 1-antitrypsin deficiency has been excluded and in those without a significant smoking history.

Excision of metastatic breast cancer from sternum and reconstruction in two patients with solitary metastatic spread.

Metastatic breast carcinoma is a relatively common clinical entity. However, the prognosis of oligometastatic and polygometastatic disease differs considerably pertaining to five-year survival. Metastatic breast carcinoma to the sternum has been described as early as 1988. We describe two cases in our institution who presented with solitary sternal metastases with a previous history of treated breast cancer. In both cases, there had been a history of previous left breast cancer treated aggressively with surgical resection and adjuvant oncological therapy and maintenance hormonal therapy. Partial sternectomy or total sternectomy for solitary metastatic sternal deposits is well established with relatively low morbidity and mortality and improvement in quality of life and possible improvement in long-term survival. Furthermore, reconstructive options are inherently dependent on extent of resection performed. These techniques can incorporate the use of sternal plates in order to approximate defects and reinforce the sternum in the setting of partial sternectomy.

Pneumatic-aorta: an unusual aetiology for stroke.

The following report describes a case in which air in the aorta led to stroke from cerebral emboli in a patient with distal oesophageal cancer. The patient presented with clinical features of a right-sided stroke. Computed tomography scans revealed air in the ascending aorta and brachiocephalic artery as a result of an oesophago-atrial fistula. The patient deteriorated and died soon after hospital admission despite conservative measures successfully dissipating the air. When encountered, emergent treatment of the underlying cause should be addressed but the outcome remains poor.

External validity of the Society of Thoracic Surgeons risk stratification tool for deep sternal wound infection after cardiac surgery in a UK population.

OBJECTIVES: Deep sternal wound infection (DSWI) is a devastating complication of cardiac surgery, with a historical incidence of 0.4-5%. Predicting which patients are at higher risk of infection may help instituting various preventive measures. Risk calculations for mortality have been used as surrogates to estimate the risk of deep sternal wound infection, with limited success. The Society of Thoracic Surgeons (STS) 2008 Risk Calculator modelled the risk of DSWI for cardiac surgical patients, but it has not been validated since its publication. We sought to assess the external validity of the STS-estimated risk of DSWI in a United Kingdom (UK) population. METHODS: Using our prospectively captured database, we retrospectively calculated the risk of DSWI for 14 036 patients undergoing valve, coronary artery bypass grafts or combined procedures between February 2001 and March 2010. DSWI was identified according to the Centre for Disease Control and Prevention definition. The receiver operator characteristic (ROC) curve was employed to test the performance of the model using the area under the ROC curve (AUROC). The calibration of the model was interrogated using the Hosmer-Lemeshow test for Goodness of Fit. RESULTS: A total of 135 (0.95%) patients developed DSWI. Although there was a statistically significant difference in the calculated risk of patients who contracted DSWI (0.44% ± 0.01) vs those who did not (0.28% ± 0.00, P < 0.0001), the AUROC of 0.699 (95% confidence interval: 0.6522-0.7414) denoted a modest discriminatory power, with the Hosmer-Lemeshow Goodness of Fit statistic (P < 0.001) suggesting poor calibration. A risk-adjusted modifier improved the calibration (P = 0.08). CONCLUSIONS: The STS risk calculator lacks adequate discriminatory power for estimating the isolated risk of developing deep sternal wound infection in a UK population. The discrimination is similar to the tool's validation c-statistic and may have a place in an integrated calculator.

Comparison of the EuroSCORE II and Society of Thoracic Surgeons 2008 risk tools.

OBJECTIVES: Risk stratification in cardiac surgery is uniquely detailed, led latterly by the EuroSCORE and the Society of Thoracic Surgeons (STS) risk calculators. The recently published EuroSCORE II (ES2) algorithms update estimated mortality in a broad spectrum of cardiac procedures. The 2008 STS tool, in comparison, predicts multiple outcomes for specific procedures. We sought to identify and compare the external validity of both contemporaneous tools in our population. METHODS: Data from our hospital database were collated for the period February 2001 to March 2010. Logistic regression coefficients from the risk calculations were applied to the data and the results presented as receiver-operating characteristic (ROC) curves. Statistical analyses were performed using the area under the ROC curve (AUROC) and the Hosmer-Lemeshow (H-L) goodness-of-fit test, with comparisons using the DeLong method. RESULTS: A total of 15 497 procedures were identified, of which 14 432 were appropriate for STS risk scoring (i.e. valve and/or graft procedures with no tricuspid valve operations etc.). For all procedures, ES2 and STS were equivalent (AUROC 0.818 vs 0.805, respectively, P = 0.343). For procedures appropriate for STS risk scoring, results were similar (AUROC ES2 vs STS, 0.816 vs 0.810, P = 0.714), whereas for procedures excluded by STS, the result was marginally worse (AUROC ES2 vs STS, 0.773 vs 0.784, P = 0.751). Goodness of fit in all cases was poor, primarily where risk was higher than 15% (H-L P < 0.0001). CONCLUSIONS: EuroSCORE II and STS both provide equivalent discrimination in predicting mortality in a British population, including those undergoing procedures for which the STS does not normally predict. Accounting for decile-grouped Hosmer-Lemeshow tests not being ideal for the assessment of calibration, both tools show good calibration for patients with low to moderate risk, with divergence from ~15% predicted risk.